Haldol (haloperidol)

Haldol tablets, liquid and injection all contain the active ingredient haloperidol. Haloperidol is a type of medicine known as an antipsychotic. It is used in the treatment of various psychiatric illnesses. Haloperidol is also available without a brand name, ie as the generic medicine.

Haloperidol may be given by injection when taking the medicine by mouth is not possible, for example to control sickness and vomiting, or to quickly control acutely disturbed behaviour.

How does it work?

Haldol tablets, liquid and injection all contain the active ingredient haloperidol. Haloperidol is a type of medicine known as an antipsychotic. It is used in the treatment of various psychiatric illnesses. Haloperidol is also available without a brand name, ie as the generic medicine.

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When used in psychiatric illness, haloperidol is sometimes described as a neuroleptic or a 'major tranquilliser', though this last term is fairly misleading, as this type of medicine is not just a tranquilliser, and any tranquillising effect is not as important as the main way it works in psychiatric illness.

Haloperidol works by blocking a variety of receptors in the brain, particularly dopamine receptors. Dopamine is a natural compound called a neurotransmitter, and is involved in transmitting messages between brain cells. Dopamine is a neurotransmitter known to be involved in regulating mood and behaviour, amongst other things.

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Psychotic illness, and particularly schizophrenia, is considered to be caused by overactivity of dopamine in the brain. Haloperidol blocks the receptors that dopamine acts on and this prevents the overactivity of dopamine in the brain. This helps to control psychotic illness.

Haloperidol improves disturbed thoughts, feelings and behaviour in various mental conditions, including schizophrenia, mania, and behavioural disorders that involve aggression or severe agitation or excitement. It produces a calming effect and controls aggression, delusions and hallucinations.

Haloperidol is used used in the long-term management of psychotic conditions such as schizophrenia. It is also used in the short-term to manage severe anxiety and severely agitated, violent or dangerous behaviour.

Haloperidol is also used to treat Tourette's syndrome, which is a condition involving involuntary muscle twitching and uncontrollable urges to utter obscene words or other noises.

Haloperidol also affects dopamine receptors in an area of the brain that controls nausea and vomiting. Vomiting is controlled by an area of the brain called the vomiting centre. The vomiting centre is responsible for causing feelings of sickness (nausea) and for the vomiting reflex. It is activated when it receives nerve messages from another area of the brain called the chemoreceptor trigger zone (CTZ) and when it receives nerve messages from the gut.

Haloperidol controls nausea and vomiting by blocking dopamine receptors found in the CTZ. This stops the CTZ from sending the messages to the vomiting centre that would otherwise cause nausea and vomiting. Haloperidol is sometimes used to provide relief from nausea and vomiting in terminal illness.

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Haloperidol is also effective in treating persistant hiccups, though how it works in this case is unclear.

How do I take it?

Haloperidol tablets and liquid can be taken either with or without food.

The dose of this medicine that is prescribed, how often to take it and how long to take it for depends on the condition being treated. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label that your pharmacist has put on the packet of medicine.

If you forget to take a dose take it as soon as you remember, unless it is nearly time for your next dose. In this case just leave out the forgotten dose and take the next dose as usual. Don't take a double dose to make up for a missed dose.

If you have been taking high doses of this medicine for a long time, for example to treat schizophrenia, you should not suddenly stop taking it unless your doctor tells you to, even if you feel better and think you don't need it any more. This is because the medicine controls the symptoms of the illness but doesn't actually cure it. This means that if you suddenly stop treatment your symptoms could come back. Stopping the medicine suddenly may also rarely cause withdrawal symptoms such as nausea, vomiting, difficulty sleeping or tremor. When long-term treatment with this medicine is stopped, it should be done gradually, following the instructions given by your doctor.

Warning!

This medicine may cause drowsiness and blurred vision. If affected do not drive or operate machinery. You should avoid drinking alcohol while taking this medicine because it can make drowsiness worse.

This medicine can occasionally cause your blood pressure to drop when you move from a lying down or sitting position to sitting or standing, especially when you first start taking the medicine. This may make you feel dizzy or unsteady. To avoid this try getting up slowly. If you do feel dizzy, sit or lie down until the symptoms pass.

Your doctor may want to check your heart function with an ECG before you start treatment with this medicine, and may want to do further checks from time to time throughout your treatment.

Antipsychotic medicines are associated with an increased risk of getting a blood clot in a vein (deep vein thrombosis) or in the lungs (pulmonary embolism). For this reason, you should consult a doctor immediately if you get any of the following symptoms, as these could suggest you have a blood clot: stabbing pains and/or unusual redness or swelling in one leg, pain on breathing or coughing, coughing up blood or sudden breathlessness.

Antipsychotic medicines can sometimes affect the ability of the body to control its core body temperature. This is more likely to be a problem in elderly people and can result in heat stroke in hot temperatures and hypothermia in cold temperatures. It is important to avoid situations that can result in you overheating or getting dehydrated. Ask your doctor or pharmacist for more advice.

Consult your doctor immediately if you experience abnormal movements, particularly of the face, lips, jaw and tongue, while taking this medicine. These symptoms may be indicative of a rare side effect known as tardive dyskinesia, and your doctor may ask you to stop taking this medicine, or decrease your dose.

Consult your doctor immediately if you experience the following symptoms while taking this medicine: high temperature (fever), pale complexion, sweating, muscle stiffness, fast heartbeat and feeling very drowsy. These symptoms may be due to a rare but serious side effect of this type of medicine, known as the neuroleptic malignant syndrome, and your treatment may need to be stopped.

Use with caution in

Elderly people with dementia. (Antipsychotic medicines have been shown to increase the risk of stroke in this group of patients. Haloperidol is not licensed or recommended for treating behavioural disturbances in elderly people with dementia).

People with risk factors for having a stroke, for example a history of stroke or mini-stroke (TIA), smoking, diabetes, high blood pressure, or a type of irregular heartbeat called atrial fibrillation.

People with other risk factors for getting a blood clot, for example smoking, being overweight, taking the contraceptive pill, being over 40, recent major surgery or being immobile for prolonged periods.

People who have had a bleed into the brain (subarachnoid haemorrhage).

People with a type of abnormal heart rhythm, seen on a heart monitoring trace (ECG) as a 'prolonged QT interval'.

People taking medicines that can cause a prolonged QT interval (your doctor will know, but see the end of this factsheet for some examples).

People with a history of abnormal heart rhythms originating in the lower chambers of the heart (ventricular arrhythmias, eg Torsades de pointes).

People with low levels of potassium in their blood (hypokalaemia).

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

The safety of this medicine during pregnancy has not been established. It should not normally be used in pregnancy, particularly in the first and third trimesters, unless considered essential by your doctor. However, doctors may sometimes prescribe this medicine to treat pregnant women with severe psychiatric illness. The dose and duration of treatment should be as low and as short as possible. If you are pregnant and your doctor has prescribed you this medicine, it is because the condition being treated with the medicine could pose more of a risk to the baby than the medicine itself. However, if the medicine is used during the third trimester it could cause side effects or withdrawal symptoms in the baby after birth and the baby may need extra monitoring because of this. If you are concerned or want any further information you should talk to your doctor or pharmacist.

If you do get pregnant while taking this medicine it is important to consult your doctor straight away for advice. If you have been taking the medicine for long periods of time, for instance to treat schizophrenia, you should not suddenly stop taking it unless your doctor tells you to, as this could cause your symptoms to come back.

This medicine passes into breast milk and may potentially have adverse effects on a nursing infant. Mothers who need to take this medicine should discuss the risks and benefits of breastfeeding during treatment with their doctor.

Label warnings

This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Uncommon (affect between 1 in 100 and 1 in 1000 people)

Raised blood prolactin (milk producing hormone) level (hyperprolactinaemia). Sometimes this can lead to symptoms such as breast enlargement or discomfort, production of milk, stopping of menstrual periods and reduced sex drive.

Raised body temperature (see warning section above).

Skin reactions, such as rashes, itching, increased sensitivity to sunlight.

Excessive sweating.

Liver problems such as jaundice or liver inflammation (hepatitis). Tell your doctor straight away if you notice any yellowing of your eyes or skin while taking this medicine.

Faster than normal heartbeat (tachycardia).

Difficulty breathing.

Confusion.

Seizures (convulsions).

Decreased numbers of white blood cells in the blood. As this may increase your susceptibility to infections you should tell your doctor if you notice any signs of infection while you are taking this medicine, for example an unexplained sore throat, mouth ulcers, high temperature (fever) or general illness. Your doctor may want you to have a blood test to check the levels of blood cells in your blood.

Unknown frequency

Prolonged erection (priapism). If you get an erection that lasts longer than four hours while taking this medicine, you should consult a doctor immediately. Treatment of this condition should not be delayed more than six hours, as this can cause damage to the erectile tissue in the penis and irreversible erectile dysfunction.

Abnormal heartbeats (arrhythmias).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

There may be an increased risk of drowsiness and sedation if haloperidol is taken with any of the following (which can also cause drowsiness):

alcohol

barbiturates, eg amobarbital, phenobarbital

benzodiazepines, eg diazepam, temazepam

indometacin

MAOI antidepressants, eg phenelzine

sedating antihistamines, eg chlorphenamine, hydroxyzine

sleeping tablets, eg zopiclone

strong opioid painkillers, eg morphine, codeine

tricyclic antidepressants, eg amitriptyline.

There may be an increased risk of an abnormal heart rhythm if haloperidol is taken in combination with other medicines that can cause a 'prolonged QT interval' on a heart monitoring trace or ECG. These include the following. They should not be taken in combination with haloperidol:

There may also be an increased risk of a prolonged QT interval if medicines that can alter the levels of salts such as potassium or magnesium in the blood, eg diuretics such as furosemide, are taken in combination with haloperidol.

This medicine may enhance the blood pressure-lowering effects of certain medicines used to treat high blood pressure (antihypertensives). If you are taking medicines for high blood pressure you should tell your doctor if you feel dizzy or faint after starting treatment with this medicine, as your blood pressure medicines may need adjusting.

Haloperidol may reduce the blood pressure lowering effect of guanethidine.

Haloperidol may oppose the effect of levodopa and medicines for Parkinson's disease that work by stimulating dopamine receptors in the brain, for example ropinirole, pergolide, bromocriptine.

Haloperidol may oppose the effect of anticonvulsant medicines used to treat epilepsy.

Haloperidol should be used with caution in people taking lithium, as this combination may possibly increase the risk of side effects. If you are taking these medicines together, your blood level of lithium should be monitored regularly. You should consult your doctor straight away if you notice any new side effects, particularly an unexplained fever, or if you become confused or disorientated, with a headache, disturbances of balance and drowsiness.

There may be an increased risk of extrapyramidal-type side effects (abnormal body movements) if this medicine is used in combination with metoclopramide.

The following medicines may increase the blood level of haloperidol, which could increase the risk of its side effects. If you are prescribed any of these medicines, your doctor may need to decrease your dose of haloperidol:

alprazolam

buspirone

chlorpromazine

fluoxetine

fluvoxamine

itraconazole

ketoconazole

quinidine

venlafaxine.

The following medicines may increase the breakdown of haloperidol by the liver, which could make it less effective. If you are prescribed any of these medicines, your doctor may need to increase your dose of haloperidol:

carbamazepine (in addition, haloperidol may increase the blood level of carbamazepine, which could increase the risk of its side effects)

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